Process for the preparation of aminotriazine derivates

Abstract: The present invention relates to a process for the preparation of aminotriazine derivatives of the formula I by the solvolysis of compounds of the formula II in the presence of gaseous hydrogen chloride in an alcoholic medium. The compounds of formula I are useful as intermediates in the manufacture of insecticides.

Description: The present invention relates to a process for the preparation of aminotriazine derivatives of the formula by the solvolysis of compounds of the formula in the presence of gaseous hydrogen chloride in an alcoholic medium. The compounds of formula I are useful intermediates in the manufacture of agrochemicals, particularly insecticides, as described in EP-A-0 314 615. A process for the preparation of aminotriazine derivatives is described in EP-A-0 433 218 in which compounds of formula II above are converted to compounds of formula I by acidification and cleavage of the -COR 4 group as carboxylic acid in the presence of aqueous HCl. Disadvantages of known processes, including that described in EP-A-0 433 218, are unsatisfactory product and volume yields for efficient industrial scale production, and instability of the end product in the reaction mixture. A further shortcoming of known processes is the establishment of an equilibrium state which cannot be shifted adequately to the product side so that the reaction remains essentially incomplete. Surprisingly it has now been found that a substantial increase in product yield and purity, and a shift in the equilibrium state is obtained by replacing aqueous hydrochloric acid by hydrogen chloride gas. Furthermore the decomposition of the end product in the reaction medium is prevented. It is the object, therefore, of the present invention to provide a process for the preparation of 4-amino-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine derivatives of the formula wherein R 1 is hydrogen, C 1 -C 12 alkyl, C 3 -C 6 cycloalkyl, C 1 -C 4 alkoxy-C 1 -C 6 alkyl, C 1 -C 2 haloalkyl, phenyl, benzyl, phenethyl, phenpropyl, phenbutyl or phenpentyl, or a phenyl, benzyl, phenethyl, phenpropyl, phenbutyl or phenpentyl radical that is mono- or di-substituted by halogen, C 1 -C 5 alkyl, C 1 -C 2 haloalkyl, methoxy and/or ethoxy; R 2 is hydrogen, C 1 -C 6 alkyl or C 3 -C 6 cycloalkyl, or is phenyl that is unsubstituted or substituted by C 1 -C 12 alkyl, halogen or by C 1 -C 12 haloalkyl, or R 1 and R 2 together form a saturated or unsaturated 3- to 7-membered carbocycle, and R 3 is hydrogen or C 1 -C 6 alkyl, by the solvolysis of compounds of the formula wherein R 1 , R 2 and R 3 are as defined in formula I, and R 4 is H, C 1 -C 4 -alkyl, C 3 -C 6 -cycloalkyl, C 1 -C 4 -alkyl substituted by 1 to 9 chlorine atoms, C 1 -C 3 -alkoxy, C 1 -C 3 -alkylthio, phenyl, pyridyl, or phenyl or pyridyl which is substituted with 1 to 3 substituents selected from the group consisting of halogen, methyl, ethyl, methoxy, methylthio and nitro, in the presence of gaseous hydrogen chloride in an alcoholic medium. The compounds of formula I may be converted directly into the free amines, for example by alkaline hydrolysis after completion of the reaction. R 1 is preferably methyl or ethyl, and more preferably methyl. R 2 is preferably H or C 1 -C 4 alkyl, and more preferably H, methyl or ethyl. R 3 is preferably H or C 1 -C 4 alkyl, and more preferably H or methyl. R 4 is preferably H or C 1 -C 4 -alkyl, and more preferably methyl or ethyl. The alcoholic medium can consist of one or more primary, secondary or tertiary alcohols. Examples are methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol or a mixture of these. Methanol is preferred. The reaction medium can be anhydrous or contain very small amounts of water so that the water content can be between 0 and 5 weight-% with respect to the acetyltriazinone of formula II. Substantially dry conditions, i.e. 0 to 3 wt-% water content are preferred, more preferably 0 to 2 wt-% with respect to the acetyltriazinone of formula II. Anhydrous conditions, i.e. 0 wt-% water content, are particularly preferred. The reaction can be conducted at a temperature between 0 °C and the boiling point of the solvent used. The preferred temperature range is 40 to 50 °C. Dry HCl gas is bubbled into the reaction mixture and unreacted HCl is recycled. The reaction conditions remain non-corrosive to the reaction vessel on account of the zero or very low water content. The process according to the invention can be conducted in a batchwise or continuous manner. Batchwise production is preferred. An almost quantitative conversion is obtained by the formation and precipitation of the aminotriazinone as its hydrogen chloride salt, combined with the formation of the ester of the displaced -COR 4 group. In the practise of the present invention, compounds of formula I, for example 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine hydrochloride, are prepared in high yield by the reaction of gaseous HCl with 6-methyl-4-acetylamino-4,5-dihydro-1,2,4-triazin-3-(2H)-one in methanol at around 45 °C. The free 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine can be obtained upon addition of an aqueous alkaline medium, e.g. NaOH. The starting compounds of formula II are available commercially or can be prepared by known methods. Prior to the preparation of compounds of formula I, it is advantageous to prepare compounds of formula II in situ in the same or very similar alcoholic medium to that used in the process according to the invention, thus avoiding arduous isolation or separation steps. The advantages of the process of the invention are as follows: i) yields of up to 99 % are obtained under optimised conditions; ii) no side products are formed; iii) improved volume yields are obtained; iv) faster reaction times are achieved, and v) there is negligible corrosion of the reaction vessel. It is a further object of the present invention to provide a process for the preparation of a compound of formula wherein R 1 is hydrogen, C 1 -C 12 alkyl, C 3 -C 6 cycloalkyl, C 1 -C 4 alkoxy-C 1 -C 6 alkyl, C 1 -C 2 haloalkyl, phenyl, benzyl, phenethyl, phenpropyl, phenbutyl or phenpentyl, or a phenyl, benzyl, phenethyl, phenpropyl, phenbutyl or phenpentyl radical that is mono- or di-substituted by halogen, C 1 -C 5 alkyl, C 1 -C 2 haloalkyl, methoxy and/or ethoxy, R 2 is hydrogen, C 1 -C 6 alkyl or C 3 -C 6 cycloalkyl, or is phenyl that is unsubstituted or substituted by C 1 -C 12 alkyl, halogen or C 1 -C 12 haloalkyl, or R 1 and R 2 together form a saturated or unsaturated 3- to 7-membered carbocycle, R 3 is hydrogen or C 1 -C 6 alkyl and Z is -N=CH-or -NH-CH 2 -, which process comprises reacting an aminotriazinone of formula wherein R 1 , R 2 and R 3 have the meanings as defined in formula (III), with an aldehyde of formula and, if desired, converting the resulting pyridyl-methyleneamino-triazinone by selective reduction into pyridyl-methylamino-triazinone, wherein the aminotriazinone of the formula I is prepared by the solvolysis of a compound of formula wherein R 1 , R 2 and R 3 are as defined in formula (III), and R 4 is H, C 1 -C 4 -alkyl, C 3 -C 6 -cycloalkyl, C 1 -C 4 -alkyl substituted by 1 to 9 chlorine atoms, C 1 -C 3 -alkoxy, C 1 -C 3 -alkylthio, phenyl, pyridyl, or phenyl or pyridyl which is substituted with 1 to 3 substituents selected from the group consisting of halogen, methyl, ethyl, methoxy, methylthio and nitro, in the presence of gaseous hydrogen chloride in an alcoholic medium. Preferred compounds of the formula III are those wherein R 1 is hydrogen, C 1 -C 6 alkyl, C 3 -C 5 cycloalkyl, phenyl or phenyl that is mono- or di-substituted by halogen, C 1 -C 3 alkyl, methoxy or ethoxy, each of R 2 and R 3 is hydrogen or C 1 -C 4 alkyl and Z is -N=CH- or -NH-CH 2 -, more preferred are those compounds of the formula III wherein R 1 is hydrogen, C 1 -C 4 alkyl, cyclopropyl or phenyl; R 2 is hydrogen, methyl or ethyl; and R 3 is hydrogen or methyl; and Z is -N=CH- or -NH-CH 2 -; most preferred is 6-methyl-4-(pyridin-3-yl-methyleneamino)-4,5-dihydro- 1 ,2,4-triazin-3(2H)-one. The following Examples demonstrate the process of the invention. Example 1: Preparation of 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine hydrochloride A suspension is prepared of 36.9 g (0.216 mol) 6-methyl-4-acetylamino-4,5-dihydro-1,2,4-triazin-3-(2H)-one in 115 g methanol (this suspension contains residual water from the solvent/educt corresponding to 0.25 mol water per mole acetyltriazinone). The suspension is heated to 45 °C and becomes a clear colourless solution. At between 45 and 50 °C a total of 11.8 g (0.324 mol) HCl are bubbled through this solution over a 2 to 3 hour period. After about 30 % of the HCl has been added the reaction mixture is seeded with 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine hydrochloride. Thereafter 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine precipitates out continuously as the hydrochloride salt. After about 2 hours stirring, the maximum conversion of 99 % is reached, the mixture is cooled to between 10 and 13 °C, filtered and dried. 34.0 g 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine hydrochloride are isolated, representing a yield of 95.8 % of theory. Example 2: Preparation of 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine A suspension is prepared of 39.9 g (0.234 mol) 6-methyl-4-acetylamino-4,5-dihydro-1,2,4-triazin-3-(2H)-one in 99 g 95 % methanol. The suspension is heated to 45 °C and becomes a clear colourless solution. At between 45 and 50 °C a total of 15.4 g (0.421 mol) HCl are bubbled through this solution over a 2 to 3 hour period. After about 30 % of the HCl has been added the reaction mixture is seeded with 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine hydrochloride. Thereafter 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine precipitates out continuously as the hydrochloride salt. After about 2 hours stirring, the maximum conversion of over 99 % is reached. The reaction mixture is brought to pH 5 by the addition of 50 % NaOH solution. The free aminotriazinone 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine is formed in an amount of 29.7 g representing 14.3 % by weight of the solution. This represents a yield of 99.2 % of theory. Example 3 Comparison aqueous vs. gaseous HCl A suspension is prepared of 6-methyl-4-acetylamino-4,5-dihydro-1,2,4-triazin-3-(2H)-one in methanol. The suspension is heated to 45°C and becomes a clear colourless solution. At between 45°C and 50°C gaseous HCl (a) or aqueous HCl (b) is added to this solution over a 2 to 3 hour period. After about 30 % of the gaseous HCl (a) or 50 % of the aqueous HCl (b) has been added the reaction mixture is seeded with 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine hydrochloride. Thereafter 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine precipitates out continuously as the hydrochloride salt. After about 2 hours stirring, the maximum conversion is reached. The reaction mixture is brought to pH 5 by the addition of 50 % NaOH solution, thereby forming free 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine. The respective yields of theory are as follows: Test No. A [mol] methanol [g] gaseous HCl [g] aqueous HCl [g] yield of theory [%] (a) 0.234 99 15.4 99.2 (b) 0.234 99 41.6 77.2 A = 6-methyl-4-acetylamino-4,5-dihydro-1,2,4-triazin-3-(2H)-one Test No. (a): This test is carried out with gaseous HCl. The maximum conversion is more than 99 %. The free 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine is formed in an amount of 29.7 g representing 14.3 % by weight of the solution. This represents a yield of 99.2 % of theory. Test No. (b): Test (a) is repeated using aqueous HCl. The maximum conversion is 77.2 %. The free 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine is formed in an amount of 23.1 g representing 10.3 % by weight of the solution. This represents a yield of 77.2 % of theory. Example 4 Preparation of 6-methyl-4-(pyridin-3-ylmethyleneamino)-4,5-dihydro-1,2,4-triazin-3(2H)-one To a suspension of 164 g of 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydr 1,2,4-triazine hydrochloride in 500 ml methanol a 50 % NaOH solution is added until a pH of 6 is reached. Now 486 g of a solution containing 22 % 3-pyridinaldehyde in water is added maintaining a temperature below 70°C. After the addition is completed the reaction mixture is kept at 65°C for two hours. Then the suspension is cooled to about 5°C, filtered and dried to yield the title compound.

Claims: A process for the preparation of 4-amino-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine derivatives of the formula wherein R 1 is hydrogen, C 1 -C 12 alkyl, C 3 -C 6 cycloalkyl, C 1 -C 4 alkoxy-C 1 -C 6 alkyl, C 1 -C 2 haloalkyl, phenyl, benzyl, phenethyl, phenpropyl, phenbutyl or phenpentyl, or a phenyl, benzyl, phenethyl, phenpropyl, phenbutyl or phenpentyl radical that is mono- or di-substituted by halogen, C 1 -C 5 alkyl, C 1 -C 2 haloalkyl, methoxy and/or ethoxy; R 2 is hydrogen, C 1 -C 6 alkyl or C 3 -C 6 cycloalkyl, or is phenyl that is unsubstituted or substituted by C 1 -C 12 alkyl, halogen or by C 1 -C 12 haloalkyl, or R 1 and R 2 together form a saturated or unsaturated 3- to 7-membered carbocycle, and R 3 is hydrogen or C 1 -C 6 alkyl, by the solvolysis of compounds of the formula wherein R 1 , R 2 and R 3 are as defined in formula I, and R 4 is H, C 1 -C 4 -alkyl, C 3 -C 6 -cycloalkyl, C 1 -C 4 -alkyl substituted by 1 to 9 chlorine atoms, C 1 -C 3 -alkoxy, C 1 -C 3 -alkylthio, phenyl, pyridyl, or phenyl or pyridyl which is substituted with 1 to 3 substituents selected from the group consisting of halogen, methyl, ethyl, methoxy, methylthio and nitro, in the presence of gaseous hydrogen chloride in an alcoholic medium. A process according to claim 1, wherein R 1 is methyl or ethyl. A process according to claim 1, wherein R 4 is H or C 1 -C 4 -alkyl. A process according to claim 1, wherein the alcoholic medium consists of one or more primary, secondary or tertiary alcohols. A process according to claim 4, wherein the alcoholic medium consists of methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol or a mixture of these. A process according to claim 5, wherein the alcoholic medium is methanol. A process according to claim 1, wherein the water content of the reaction medium is between 0 and 5 weight-% with respect to the acetyltriazinone of formula II. A process according to claim 7, wherein the reaction is carried out under anhydrous conditions. A process according to claim 1, wherein the reaction is conducted at a temperature between 0 °C and the boiling point of the solvent used. A process according to claim 1, wherein in the compound of the formula (II) R 1 and R 4 are methyl, R 2 and R 3 are hydrogen and the reaction is conducted at a temperature between 45°C and 50°C in methanol containing 5% by weight water. A process for the preparation of a compound of formula wherein R 1 is hydrogen, C 1 -C 12 alkyl, C 3 -C 6 cycloalkyl, C 1 -C 4 alkoxy-C 1 -C 6 alkyl, C 1 -C 2 haloalkyl, phenyl, benzyl, phenethyl, phenpropyl, phenbutyl or phenpentyl, or a phenyl, benzyl, phenethyl, phenpropyl, phenbutyl or phenpentyl radical that is mono- or di-substituted by halogen, C 1 -C 5 alkyl, C 1 -C 2 haloalkyl, methoxy and/or ethoxy; R 2 is hydrogen, C 1 -C 6 alkyl or C 3 -C 6 cycloalkyl, or is phenyl that is unsubstituted or substituted by C 1 -C 12 alkyl, halogen or C 1 -C 12 haloalkyl, or R 1 and R 2 together form a saturated or unsaturated 3- to 7-membered carbocycle; R 3 is hydrogen or C 1 -C 6 alkyl and Z is -N=CH- or -NH-CH 2 -, which process comprises reacting an aminotriazinone of formula wherein R 1 , R 2 and R 3 have the meanings as defined in formula (III), with an aldehyde of formula and, if desired, converting the resulting pyridyl-methyleneamino-triazinone by selective reduction into pyridyl-methylamino-triazinone, wherein the aminotriazinone of the formula I is prepared by the solvolysis of a compound of formula wherein R 1 , R 2 and R 3 are as defined in formula (III); and R 4 is H, C 1 -C 4 -alkyl, C 3 -C 6 -cycloalkyl, C 1 -C 4 -alkyl substituted by 1 to 9 chlorine atoms, C 1 -C 3 -alkoxy, C 1 -C 3 -alkylthio, phenyl, pyridyl, or phenyl or pyridyl which is substituted with 1 to 3 substituents selected from the group consisting of halogen, methyl, ethyl, methoxy, methylthio and nitro, in the presence of gaseous hydrogen chloride in an alcoholic medium, as in claim 1. A process according to claim 11 wherein R 1 is hydrogen, C 1 -C 6 alkyl, C 3 -C 5 cycloalkyl, phenyl or phenyl that is mono- or di-substituted by halogen, C 1 -C 3 alkyl, methoxy or ethoxy, each of R 2 and R 3 is hydrogen or C 1 -C 4 alkyl and Z is -N=CH- or -NH-CH 2 -. A process according to claim 12 wherein R 1 is hydrogen, C 1 -C 4 alkyl, cyclopropyl or phenyl; R 2 is hydrogen, methyl or ethyl; and R 3 is hydrogen or methyl; and Z is -N=CH-or -NH-CH 2 -. A process according to claim 13 wherein the compound of formula m is 6-methyl-4-(pyridin-3-ylmethyleneamino)-4,5-dihydro-1,2,4-triazin-3(2H)-one.

Inventors: RAPOLD THOMAS DR, SENN MARCEL, RAPOLD, THOMAS, DR., SENN, MARCEL
Applicants: CIBA GEIGY AG, NOVARTIS AG
Application year: 1994
Main classification: C07D253
IPC codes: C07D401, C07B61, A01N43, B01J25, C07D253